1. Field of the Invention
The present invention relates to a self-locking agent to be applied to an engaging part of a fastening device to secure that part by engaging and also to a fastening device coated with the self-locking agent.
2. Prior Art
Adhesives to be used for securing the engaging part of a fastening device by bonding generally include the following adhesives (1) to (3):
(1) an anaerobic adhesive mainly comprising an acrylic or methacrylic ester and a polymerization initiator,
(2) a precoat-type adhesive prepared by microencapsulating the same anaerobic adhesive as the above-described one (1), making the microcapsules with a catalyst, filler, binder, etc., applying the resulting mixture to the engaging part of a fastening device and drying it, and
(3) a precoat-type adhesive prepared by mixing microcapsules of an epoxy polymer with a hardener, filler and binder, applying the mixture to the engaging part of a fastening device and drying it.
However, these prior art techniques have each problems which will now be described.
The adhesive (1) is difficult to apply to a fastening device in a predetermined amount, because it is liquid. Further it is also difficult and costly to incorporate an application for the adhesive into the production line. In addition, the hardening of the adhesive when applied to, for example, a resin screw is insufficient, since the presence of a metal ion is indispensable for the hardening of the anaerobic adhesive. Since the resin squeezed out of the threaded part will not easily be hardened, it says or volatilizes to adhere to other parts, thus exerting a bad influence on the quality of the product.
The precoat-type adhesive (2) is one developed to solve the problems of the adhesive (1). Although the workability thereof was improved, the quality of the product is deteriorated when no metal ion is present on the surface of an object, since a hardening adhesive composition similar to the composition (1) is used.
The precoat-type adhesive (3) is one improved in the workability in application and the hardenability of the squeezed resin, but irritates the skin and has toxicity such as mutagenicity, since it contains an aliphatic or alicyclic polyamine used as the hardener. Further its thermal resistance and long-term stability are insufficient.
An object of the present invention is to overcome the above-described defects of the prior art techniques and, in particular, to provide a self-locking agent for a fastening device which has excellent thermal resistance and storage stability and also a fastening device coated with the self-locking agent.